(a) Field of the Invention
The present invention relates to an organic light emitting diode (“OLED”) display and a manufacturing method thereof.
(b) Description of the Related Art
Recently, as demands for lighter or thinner monitors or TVs have been increasing, cathode ray tubes (“CRTs”) are being replaced by liquid crystal displays (“LCDs”).
However, as light-receiving devices, the LCDs are disadvantageous in that they require a light source such as a backlight and have many limitations in terms of response speed and viewing angle.
Recently, OLED displays have received much attention as display devices that can overcome such limitations of the LCDs.
The OLED display includes two electrodes and an emission layer sandwiched therebetween, in which electrons injected from one electrode and holes injected from the other electrode are recombined in the emission layer to form excitons, and as the excitons release energy, the OLED display is illuminated.
The OLED display is a self-emission type of display that does not require a light source such as a backlight, so it is advantageous in terms of power consumption. Furthermore, the OLED display has good response speed, viewing angle and contrast ratio.
The OLED display includes a plurality of pixels such as red pixels, blue pixels and green pixels. A full color spectrum can be expressed by combining the various red pixels, blue pixels and green pixels.
In this case, the red pixel, the blue pixel and the green pixel include a red emission layer, a blue emission layer and a green emission layer, respectively, to express color. The emission layers may be deposited pixel-by-pixel using a fine shadow mask. However, as the size of the display device is increased, there is a limitation in depositing such emission layers at each pixel when using the fine shadow mask.
Therefore, a technique has been proposed in which the red emission layer, the blue emission layer and the green emission layer are sequentially stacked on the entire display device using an open mask to emit white light. Color filters are disposed at positions where the emitted light passes through to thus express red, green and blue colors by pixel.
However, due to the limitation in color reproducibility of the color filters themselves, light that passes through the color filters is bound to have color reproducibility which at best may be the same as, or more likely lower than the color reproducibility of the color filters. As a result of the limitation in color reproducibility of the color filters, such high color reproducibility as required by the National Television Systems Committee (“NTSC”) is difficult to achieve from the light that passes through the color filters.